Another climate catch-22

Now here’s an item to make you grind your molars: New Anti-Smog Restrictions Could Warm Planet:

The Environmental Protection Agency’s proposal to tighten the ozone standard for smog will have an unfortunate side effect: Because of a quirk of atmospheric chemistry, those measures will hasten global warming.

There’s no question that smog is a hazard that deserves attention. Lydia Wegman of the EPA says the new ozone limits would have significant health benefits.

Less smog means fewer asthma attacks, fewer kids in the hospital, fewer days of lost school, “and we also believe that we can reduce the risk of early death in people with heart and lung disease,” she says.

Here’s the tough part: The way many states and localities will reduce smog is by cracking down on the chemicals that produce ozone. And those include nitrogen oxides, or NOx.

The Net Effect Could Make Global Warming Worse

But Jason West at the University of North Carolina in Chapel Hill says that when you reduce NOx, you don’t just reduce ozone; you change the chemistry of the atmosphere in such a way that you end up increasing the amount of methane in the air. And methane is a potent gas when it comes to global warming.

“By reducing NOx, the net effect is you make global warming worse,” West says.

In fact, you could make warming a lot worse. If you got rid of all NOx and a related sulfur compound, that action alone would be enough to increase the Earth’s temperature by 2 degrees Celsius – and that’s in the danger zone for the climate, according to many scientists and governments.

Ouch.

I said this was “another” climate catch-22. The main one is alluded to in the above quote: The reduction in sulfate aerosols when we reduce our coal usage.

Mining and burning coal has a lot of side effects. It emits CO2, particulate matter, mercury, and other bad things. One of the things it emits is sulfate aerosols, which actually have a cooling effect and partially offset the warming from all that coal-use-triggered CO2. This puts us in a truly nasty corner. We have to reduce our CO2 emissions a lot, and CO2 from coal burning is such a large portion of those emissions that we have to either dramatically curtail our coal burning or we have to pull on hell of a techno-rabbit out of out hat and figure out how to make CCS (carbon capture and sequestration) not only work, but work at an acceptable cost, and then roll it out on a large scale to existing coal plants, which were never designed or located with CCS in mind.

My conclusion: The hurdles are simply too high for CCS to ride to the rescue, so we have to use a lot less coal. That will almost instantly reduce the atmospheric aerosols, since they stay around for days to months (unless we’re talking about a major volcano eruption, in which case it’s longer). And that results in a jump in global warming because CO2 has a vastly longer atmospheric lifetime, so the CO2 we’ve already emitted is still up there doing its thing. Even without the drop in aerosols, a big reduction in CO2 emissions would still leave us with decades of continued warming, thanks to all the warming that’s “in the pipeline”.

You can see the IPCC’s table of radiative forcings for various anthropogenic emissions here.

If you prefer the graphic: